Silicon (Si) is one of most common elements in the universe by mass and it most exists in compound forms of sands, dusts, silicon dioxide (silica), or silicates, etc. Pure crystal silicon is a gray color and brittle in nature. Silicon has atomic number 14, an atomic weight of 28.09, and a density of 2.33 g/cm3. Silicon has a diamond cubic crystal structure at room temperature, a melting point of 1310° C., a boiling point of 2357° C. Furthermore, silicon has a linear coefficient of thermal expansion (CTE) of 2.49 μm/m-° C. at temperature 25.0° C.
Silicon is a semiconductor and plays a key role in the modern world economy. In fact, the entire modern semiconductor microelectronics industry is established on silicon base. Silicon is widely used for integrated circuits, chips, logic electronics devices, and memory electronics devices. Silicon and its compounds are not only used for forming the substrate where the semiconductor chips are built on but also for the function units or layer for transistors and stacking structures such as silicon electrode, silicon dioxide dielectric layers, and silicon nitride mask layers, inside the chips and integrated circuits (IC).
In recent years, high-k metal gate (HKMG) transistor technology has been developed and applied to 45 nm and below to manufacture IC devices for a wide variety of high performance and low power applications such as graphics, networking, and wireless mobile applications. One of the key tasks for high-k metal gate (HKMG) is to find out suitable new metal materials and reliable film formation methods to control of the channel with high on currents and low leakage current and keep the integrity of complex structures. Hf, TiAl, TiN, TiAlN, TiSiN, TaAlN, TaSiN, and rare earth metals are reported to be used as metal gate materials. Recently, much attention has been paid to utilize silicon to as metal gate structure materials due to its unique chemical and physical properties and natural connection to the semiconductor technologies built on the silicon.
Silicon and silicon nitride layers beyond the substrate inside the IC and chips are traditionally formed through chemical vapor deposition (CVD) method. As the microelectronics industry drives the miniaturization of devices and circuits towards nanometer dimension utilizing 45 nm and below technologies, ever-increasing stringent demands have been placed on the precision and minimum impact device integrity of film/structure formation methods. Sputtering is a mechanism by which atoms are removed from the surface of a material (target) as a result of collision with high-energy ions through a physical vapor deposition (PVD) technique wherein atoms or molecules are ejected from a target material by high-energy ions bombardment so that the ejected atoms or atom clusters can condense on a substrate as a thin film. Sputtering has more precise control of the transportation and deposition of mass atoms and has less thermal impact on the deposited film structure than a CVD process. Si sputtering target through a PVD process is becoming more widely used to silicon layers such metal gate electrode and its compound structure layers such as silicon nitride and silicon carbides inside microelectronics integrated circuits and communication devices for a wide variety of high performance and low power applications such as graphics, networking, and wireless mobile applications.